Difluoro-derivative compounds and liquid crystal compositions containing them

ABSTRACT

The present invention provides a difluoro-derivative compound of the formula R 1  --(A 1  --Y 1 ) m  --A 2  --CF═CF--C.tbd.C--A 3  --(Y 2  --A 4 ) n  --R 2  (wherein each of A 1  to A 4  is a trans-1,4-cyclohexylene group, a 1,4-cyclohexenylene group or a 1,4-phenylene group, each of m and n is 0 or 1, and each of R 1  and R 2  is a C 1-10  alkyl group, a halogen atom or a cyano group). 
     The compound of the present invention has a low viscosity and is stable against lights, and a high speed response is expected by using it for a liquid crystal composition.

TECHNICAL FIELD

The present invention relates to difluoro-derivative compounds,compounds having a liquid crystal property selected from suchderivatives, liquid crystal compositions containing thedifluoro-derivative compounds, and liquid crystal electro-opticaldevices using the liquid crystal compositions.

BACKGROUND ART

Liquid crystal display devices have been used for watches and electroniccalculators and in recent years for various applications includingmeasuring devices, automobile meters, copying machines, cameras, displaydevices for office appliances and display devices for consumer products.Accordingly, various functions including a wide temperature range foroperation, a low voltage for driving, a high response speed, a highcontrast ratio, a wide visual angle and chemical stability, are requiredfor such liquid display devices.

However, at present, there is no single material which by itselfsatisfies all of such requirements, and it is common to satisfy suchrequirements by a liquid crystal composition prepared by mixing aplurality of liquid crystal materials and non-liquid crystal materials.Accordingly, it is desired to develop a liquid crystal material or anon-liquid crystal material which is excellent in one or more functions,if not in all the required functions.

In the field of the display device using liquid crystal, it is desiredto improve its performance. For this purpose, low voltage driving,highly fine display, a high contrast ratio, a wide visual anglecharacteristic, a low temperature response characteristic and a widerange of driving temperature are, for example, desired. These functionshave a tendency such that when some of them are improved, others have tobe sacrificed.

Recently, improvement of a response speed is particularly desired. Forexample, in driving the device by an electrical cell, low voltage driveand high speed response are desired; in e.g. the office appliances,highly fine display and high speed response are required; and in thedisplay for automobiles, low temperature response or high speed responsewithin a wide temperature range for operation is desired.

In this respect, several methods for improvement are conceivable. One ofthem is to adopt a liquid crystal composition having a low viscosity.Namely, if the viscosity of the liquid crystal composition is reduced,the response speed can be improved so that a display will be possible ata practical speed even at a low temperature. Further, if the responsespeed may be at a level equal to the conventional speed, it will bepossible to drive the device at a lower voltage, or a higher duty driveor highly fine drive, will be possible.

For such a purpose, a p,p'-disubstituted difluorostilbene compound hasbeen proposed, as disclosed at the 16th Liquid Crystal DiscussionMeeting. This compound has a chemical structure as shown by thefollowing formula (3): ##STR1## provided that in the formula (3), eachof R^(A) and R^(B) is a n-alkyl group, a n-alkoxy group or an-alkoxycarbonyl group.

The compound of this formula (3) has a low viscosity and has thestability against light improved over a stilbene compound which is notsubstituted by fluorine. However, as compared with commonly employedliquid crystal compounds, its stability against light is still poor,whereby in many cases, the useful environment has been rather limited,or it has been required to use an ultraviolet ray-preventive film.

Accordingly, a liquid crystal material having a low viscosity and havinga high stability against light, has been desired.

It is an object of the present invention to provide a novel materialthereby to solve the above problem.

The present invention provides a difluoro-derivative compound of thefollowing formula (1):

    R.sup.1 --(A.sup.1 --Y.sup.1).sub.m --A.sup.2 CF═CF--C.tbd.C--A.sup.3 --(Y.sup.2 --A.sup.4).sub.n --R.sup.2                     ( 1)

provided that in the formula (1), A¹, A², A³, A⁴, Y¹, Y², m, n, R¹ andR² are as follows:

each of A¹, A², A³ and A⁴, which are independent from one another, is acyclic group selected from a trans-1,4-cyclohexylene group, a1,4-cyclohexenylene group and a 1,4-phenylene group, wherein each ofsuch cyclic groups is unsubstituted or substituted by one or morehalogen atoms or cyano groups, one or more ═CH-- groups constitutingrings of such cyclic groups may be substituted by nitrogen atoms, andone or more --CH₂ -- groups constituting rings of such cyclic groups maybe substituted by oxygen atoms or sulfur atoms;

each of Y¹ and Y², which are independent from each other, is --COO--,--OCO--, --C.tbd.C--, --CH₂ CH₂ --, --CH═CH--, --OCH₂ --, --CH₂ O-- or asingle bond;

each of m and n, which are independent from each other, is 0 or 1; and

each of R¹ and R² which are independent from each other, is a C₁₋₁₀alkyl group, a halogen atom or a cyano group, provided that in the caseof the alkyl group, an oxygen atom, a carbonyloxy group or anoxycarbonyl group may be interposed in a carbon-carbon bond of the alkylgroup or in a carbon-carbon bond between this alkyl group and theadjacent cyclic group, some of carbon-carbon bonds in the alkyl groupmay be triple bonds or double bonds, one --CH₂ -- group in the alkylgroup may be substituted by a carbonyl group, and some or all ofhydrogen atoms in the alkyl group may be substituted by fluorine atoms.

The present invention also provides a difluoro-derivative compound ofthe formula (2) R¹ --A² --CF═CF--C.tbd.C--A³ --R² (wherein A², A³, R¹and R² are as defined with respect to the formula (1)), a compoundhaving a liquid crystal property selected from such derivatives, and aliquid crystal composition containing a compound of the formula (1) or(2).

Further, the present invention provides a liquid crystal electro-opticaldevice having a compound of the formula (1) or (2) interposed betweensubstrates provided with electrodes.

The compound of the formula (1) of the present invention has a lowviscosity, and it is excellent in compatibility with other liquidcrystals or non-liquid crystals and is a material which is chemicallystable particularly against light.

The following compounds may be mentioned to show the specific structuresof the compound of the present invention. As a typical compound havingtwo rings, the following compound may be mentioned.

    R.sup.1 --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --R.sup.2  ( 4)

More specifically, the compound of the formula (4) includes thefollowing compounds. In the following description, "--Ph--" represents a1,4-phenylene group, "--Cy--" represents a trans-1,4-cyclohexylene groupand "--Ch--" represents a 1,4-cyclohexenylene group. This applies notonly to the compound of the formula (4) but also to other compounds. Thecyclohexenylene group is preferably a 4-substituted 1-cyclohexenylgroup.

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ph--R.sup.2              ( 4A) ##STR2##

The following compound may be mentioned as a compound of the formula(4A) wherein the 1,4-phenylene groups are replaced bytrans-1,4-cyclohexylene groups;

    R.sup.1 --Cy--CF═CF--C.tbd.C--Cy--R.sup.2              ( 4B) ##STR3##

Further, the following compound may be mentioned as a compound of theformula (4A) wherein the 1,4-phenylene groups are replaced by1,4-cyclohexylene groups;

    R.sup.1 --Ch--CF═CF--C.tbd.C--Ch--R.sup.2              ( 4C) ##STR4##

Further, the following compound may be mentioned as a compound of theformula (4A) wherein one of the 1,4-phenylene groups is replaced by atrans-1,4-cyclohexylene group;

    R.sup.1 --Ph--CF═CF--C.tbd.C--Cy--R.sup.2              ( 4D) ##STR5##

Further, the following compound may be mentioned as a compound of theformula (4A) wherein one of the 1,4phenylene groups is replaced by a1,4-cyclohexenylene group;

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ch--R.sup.2              ( 4E) ##STR6##

Further, the following compound may be mentioned as a compound of theformula (4A) wherein one of the 1,4-phenylene groups is replaced by atrans-1,4-cyclohexylene group and the other is replaced by a1,4-cyclohexenylene group;

    R.sup.1 --Cy--CF═CF--C.tbd.C--Ch--R.sup.2              ( 4F) ##STR7##

Further, the following compound may be mentioned as a compound of theformula (4A) wherein the 1,4-phenylene groups are phenylene groups withsome of hydrogen atoms replaced by fluorine atoms. Here, "PhF"represents a monofluoro-1,4-phenylene group or apolyfluoro-1,4-phenylene group, provided that each of j and k which areindependent from each other, is an integer of from 1 to 4.

    R.sup.1 --PhF--CF═CF--C.tbd.C--PhF--R.sup.2            ( 4G) ##STR8##

Further, the following compounds may be mentioned as compounds havingthree rings:

    R.sup.1 --A.sup.1 --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --R.sup.2( 5)

    R.sup.1 --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --A.sup.4 --R.sup.2( 6)

More specifically, the following compounds may be mentioned as thecompound of the formula (5):

    R.sup.1 --Ph--Ph--CF═CF--C.tbd.C--Ph--R.sup.2          ( 5A) ##STR9##

    R.sup.1 --Cy--Cy--CF═CF--C.tbd.C--Cy--R.sup.2          ( 5B)

    R.sup.1 --Ch--Ch--CF═CF--C.tbd.C--Ch--R.sup.2          ( 5C)

    R.sup.1 --Ph--Ph--CF═CF--C.tbd.C--Cy--R.sup.2          ( 5D)

    R.sup.1 --Ph--Ph--CF═CF--C.tbd.C--Ch--R.sup.2          ( 5E)

    R.sup.1 --Cy--Cy--CF═CF--C.tbd.C--Ph--R.sup.3          ( 5F)

    R.sup.1 --Cy--Cy--CF═CF--C.tbd.C--Ch--R.sup.2          ( 5G)

    R.sup.1 --Ch--Ch--CF═CF--C.tbd.C--Ph--R.sup.2          ( 5H)

    R.sup.1 --Ch--Ch--CF═CF--C.tbd.C--Cy--R.sup.2          ( 5I)

    R.sup.1 --Cy--Ph--CF═CF--C.tbd.C--Ph--R.sup.2          ( 5J)

    R.sup.1 --Ph--Cy--CF═CF--C.tbd.C--Ph--R.sup.2          ( 5K)

    R.sup.1 --Ph--Ch--CF═CF--C.tbd.C--Ph--R.sup.2          ( 5L)

    R.sup.1 --Ch--Ph--CF═CF--C.tbd.C--Ph--R.sup.2          ( 5M)

    R.sup.1 --Cy--Ch--CF═CF--C.tbd.C--Ph--R.sup.2          ( 5N)

    R.sup.1 --CH--Cy--CF═CF--C.tbd.C--Ph--R.sup.2          ( 5O)

    R.sup.1 --Ph--Cy--CF═CF--C.tbd.C--Cy--R.sup.2          ( 5P)

    R.sup.1 --Cy--Ph--CF═CF--C.tbd.C--Cy--R.sup.2          ( 5Q)

    R.sup.1 --Ph--Ch--CF═CF--C.tbd.C--Cy--R.sup.2          ( 5R)

    R.sup.1 --CH--Ph--CF═CF--C.tbd.C--Cy--R.sup.2          ( 5S)

    R.sup.1 --Cy--Ch--CF═CF--C.tbd.C--Cy--R.sup.2          ( 5T)

    R.sup.1 --Ch--Cy--CF═CF--C.tbd.C--Cy--R.sup.2          ( 5U)

    R.sup.1 --Ph--Cy--CF═CF--C.tbd.C--Ch--R.sup.2          ( 5V)

    R.sup.1 --Cy--Ph--CF═CF--C.tbd.C--Ch--R.sup.2          ( 5W)

    R.sup.1 --Ph--Ch--CF═CF--C.tbd.C--Ch--R.sup.2          ( 5X)

    R.sup.1 --Ch--Ph--CF═CF--C.tbd.C--Ch--R.sup.2          ( 5Y)

    R.sup.1 --Cy--Ch--CF═CF--C.tbd.C--Ch--R.sup.2          ( 5Z)

    R.sup.1 --Ch--Cy--CF═CF--C.tbd.C--Ch--R.sup.2          ( 5a)

    R.sup.1 --Ph--PhF--CF═CF--C.tbd.C--Ph--R.sup.2         ( 5b)

    R.sup.1 --Cy--PhF--CF═CF--C.tbd.C--Ph--R.sup.2         ( 5c)

    R.sup.1 --Ch--PhF--CF═CF--C.tbd.C--Ph--R.sup.2         ( 5d)

    R.sup.1 --Ph--PhF--CF═CF--C.tbd.C--Cy--R.sup.2         ( 5e)

    R.sup.1 --Cy--PhF--CF═CF--C.tbd.C--Cy--R.sup.2         ( 5f)

    R.sup.1 --Ch--PhF--CF═CF--C.tbd.C--Cy--R.sup.2         ( 5g)

    R.sup.1 --Ph--PhF--CF═CF--C.tbd.C--Ch--R.sup.2         ( 5h)

    R.sup.1 --Cy--PhF--CF═CF--C.tbd.C--Ch--R.sup.2         ( 5i)

    R.sup.1 --Ch--PhF--CF═CF--C.tbd.C--Ch--R.sup.2         ( 5j)

More specifically, the following compounds may be mentioned as thecompound of the formula (6):

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ph--Ph--R.sup.2          ( 6A) ##STR10##

    R.sup.1 --Cy--CF═CF--C.tbd.C--Cy--Cy--R.sup.2          ( 6B)

    R.sup.1 --Ch--CF═CF--C.tbd.C--Ch--Ch--R.sup.2          ( 6C)

    R.sup.1 --Cy--CF═CF--C.tbd.C--Ph--Ph--R.sup.2          ( 6D)

    R.sup.1 --Ch--CF═CF--C.tbd.C--Ph--Ph--R.sup.2          ( 6E)

    R.sup.1 --Ph--CF═CF--C.tbd.C--Cy--Cy--R.sup.2          ( 6F)

    R.sup.1 --Ch--CF═CF--C.tbd.C--Cy--Cy--R.sup.2          ( 6G)

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ch--Ch--R.sup.2          ( 6H)

    R.sup.1 --Cy--CF═CF--C.tbd.C--Ch--Ch--R.sup.2          ( 6I)

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ph--Cy--R.sup.2          ( 6J)

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ph--Ch--R.sup.2          ( 6K)

    R.sup.1 --Ph--CF═CF--C.tbd.C--PhF--Ph--R.sup.2         ( 6L)

    R.sup.1 --Ph--CF═CF--C.tbd.C--PhF--Cy--R.sup.2         ( 6M)

    R.sup.1 --Ph--CF═CF--C.tbd.C--PhF--Ch--R.sup.2         ( 6N)

Furthermore, the following compounds may be mentioned as compoundshaving three rings wherein Y¹ and Y² between rings are changed to otherthan a single bond:

    R.sup.1 --Ph--Ph--C.tbd.C--Ph--CF═CF--C.tbd.C--Ph--R.sup.2( 7A)

    R.sup.1 --Ph--CH.sub.2 CH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--R.sup.2( 7B)

    R.sup.1 --Ph--OCH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--R.sup.2( 7C)

    R.sup.1 --Ph--CH.sub.2 O--Ph--CF═CF--C.tbd.C--Ph--R.sup.2( 7D)

    R.sup.1 --Ph--COO--Ph--CF═CF--C.tbd.C--Ph--R.sup.2     ( 7E)

    R.sup.1 --Ph--OCO --Ph--CF═CF--C.tbd.C--Ph--R.sup.2    ( 7F)

    R.sup.1 --Ph--C.tbd.C--Ph--CF═CF--C.tbd.C--Ph--R.sup.2 ( 7G)

    R.sup.1 --Ph--CH.sub.2 CH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--R.sup.2( 7H)

    R.sup.1 --Ph--OCH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--R.sup.2( 7I)

    R.sup.1 --Ph--CH.sub.2 O--Ph--CF═CF--C.tbd.C--Ph--R.sup.2( 7J)

    R.sup.1 --Ph--COO--Ph--CF═CF--C.tbd.C--Ph--R.sup.2     ( 7K)

    R.sup.1 --Ph--OCO--Ph--CF═CF--C.tbd.C--Ph--R.sup.2     ( 7L)

    R.sup.1 --Ph--C.tbd.C--Ph--CF═CF--C.tbd.C--Ph--R.sup.2 ( 7M)

    R.sup.1 --Ph--CH.sub.2 CH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--R.sup.2( 7N)

    R.sup.1 --Ph--OCH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--R.sup.2( 7O)

    R.sup.1 --Ph--CH.sub.2 O--Ph--CF═CF--C.tbd.C--Ph--R.sup.2( 7P)

    R.sup.1 --Ph--COO--Ph--CF═CF--C.tbd.C--Ph--R.sup.2     ( 7Q)

    R.sup.1 --Ph--OCO--Ph--CF═CF--C.tbd.C--Ph--R.sup.2     ( 7R)

    R.sup.1 --Ph--CF═CF--.tbd.C--Ph--C.tbd.C--Ph--R.sup.2  ( 7S)

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ph--CH.sub.2 CH.sub.2 --Ph--R.sup.2( 7T)

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ph--OCH.sub.2 --Ph--R.sup.2( 7U)

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ph--CH.sub.2 O--Ph--R.sup.2( 7V)

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ph--COO--Ph--R.sup.2     ( 7W)

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ph--OCO--Ph--R.sup.2     ( 7X)

Further, the following compound may be mentioned as compound having fourrings:

    R.sup.1 --A.sup.1 --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --A.sup.4 --R.sup.2                                                 ( 8)

More specifically, the following compounds may be mentioned as thecompound of the formula (8):

    R.sup.1 --Ph--Ph--CF═CF--C.tbd.C--Ph--Ph--R.sup.2      ( 8A) ##STR11##

    R.sup.1 --Cy--Cy--CF═CF--C.tbd.C--Cy--Cy--R.sup.2      ( 8B)

    R.sup.1 --Ch--Ch--CF═CF--C.tbd.C--Ch--Ch--R.sup.2      ( 8C)

    R.sup.1 --Cy--Ph--CF═CF--C.tbd.C--Ph--Cy--R.sup.2      ( 8D)

    R.sup.1 --Ch--Ph--CF═CF--C.tbd.C--Ph--Ch--R.sup.2      ( 8E)

    R.sup.1 --Ph--Cy--CF═CF--C.tbd.C--Cy--Ph--R.sup.2      ( 8F)

    R.sup.1 --Ch--Cy--CF═CF--C.tbd.C--Cy--Ch--R.sup.2      ( 8G)

    R.sup.1 --Ph--Ch--CF═CF--C.tbd.C--Ch--Ph--R.sup.2      ( 8H)

    R.sup.1 --Cy--Ch--CF═CF--C.tbd.C--Ch--Cy--R.sup.2      ( 8I)

    R.sup.1 --Ph--PhF--CF═CF--C.tbd.C--PhF--Ph--R.sup.2    ( 8J)

    R.sup.1 --Cy--PhF--CF═CF--C.tbd.C--PhF--Cy--R.sup.2    ( 8K)

    R.sup.1 --Ch--PhF--CF═CF--C.tbd.C--PhF--Ch--R.sup.2    ( 8L)

    R.sup.1 --Ph--Ph--CF═CF--C.tbd.C--Cy--Cy--R.sup.2      ( 8M)

    R.sup.1 --Ph--Ph--CF═CF--C.tbd.C--Ch--Ch--R.sup.2      ( 8N)

    R.sup.1 --Cy--Cy--CF═CF--C.tbd.C--Ch--Ch--R.sup.2      ( 8O)

    R.sup.1 --Cy--Ph--CF═CF--C.tbd.C--Cy--Ph--R.sup.2      ( 8P)

    R.sup.1 --Ch--Ph--CF═CF--C.tbd.C--Ch--Ph--R.sup.2      ( 8Q)

    R.sup.1 --Ch--Cy--CF═CF--C.tbd.C--Ch--Cy--R.sup.2      ( 8R)

Furthermore, the following compounds may be mentioned as compoundshaving four rings wherein Y¹ and Y² between rings are changed to otherthan a single bond;

    R.sup.1 --Ph--C.tbd.C--Ph--CF═CF--C.tbd.C--Ph--Ph--R.sup.2( 9A)

    R.sup.1 --Ph--CH.sub.2 CH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--Ph--R.sup.2( 9B)

    R.sup.1 --Ph--OCH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--Ph--R.sup.2( 9C)

    R.sup.1 --Ph--CH.sub.2 O--Ph--CF═CF--C.tbd.C--Ph--Ph--R.sup.2( 9D)

    R.sup.1 --Ph--COO--Ph--CF═CF--C.tbd.C--Ph--Ph--R.sup.2 ( 9E)

    R.sup.1 --Ph--OCO--Ph--CF═CF--C.tbd.C--Ph--Ph--R.sup.2 ( 9F)

    R.sup.1 --Ph--C.tbd.C--Ph--CF═CF--C.tbd.C--Ph--Cy--R.sup.2( 9G)

    R.sup.1 --Ph--CH.sub.2 CH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--Cy--R.sup.2( 9H)

    R.sup.1 --Ph--OCH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--Cy--R.sup.2( 9I)

    R.sup.1 --Ph--CH.sub.2 O--Ph--CF═CF--C.tbd.C--Ph--Cy--R.sup.2( 9J)

    R.sup.1 --Ph--COO--Ph--CF═CF--C.tbd.C--Ph--Cy--R.sup.2 ( 9K)

    R.sup.1 --Ph--OCO--Ph--CF═CF--C.tbd.C--Ph--Cy--R.sup.2 ( 9L)

    R.sup.1 --Ph--C.tbd.C--Ph--CF═CF--C.tbd.C--Ph--Ch--R.sup.2( 9M)

    R.sup.1 --Ph--CH.sub.2 CH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--Ch--R.sup.2( 9N)

    R.sup.1 --Ph--OCH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--Ch--R.sup.2( 9O)

    R.sup.1 --Ph--CH.sub.2 O--Ph--CF═CF--C.tbd.C--Ph--Ch--R.sup.2( 9P)

    R.sup.1 --Ph--COO--Ph--CF═CF--C.tbd.C--Ph--Ch--R.sup.2 ( 9Q)

    R.sup.1 --Ph--OCO--Ph--CF═CF--C.tbd.C--Ph--Ch--R.sup.2 ( 9R)

    R.sup.1 --Ph--Ph--CF═CF--C.tbd.C--Ph--C.tbd.C--Ph--R.sup.2( 9S)

    R.sup.1 --Ph--CF═CF--C.tbd.C--Ph--CH.sub.2 CH.sub.2 --Ph--R.sup.2( 9T)

    R.sup.1 --Ph--Ph--CF═CF--C.tbd.C--Ph--OCH.sub.2 --Ph--R.sup.2( 9U)

    R.sup.1 --Ph--Ph--CF═CF--C.tbd.C--Ph--CH.sub.2 O--Ph--R.sup.2( 9V)

    R.sup.1 --Ph--Ph--CF═CF--C.tbd.C--Ph--COO--Ph--R.sup.2 ( 9W)

    R.sup.1 --Ph--Ph--CF═CF--C.tbd.C--Ph--OCO--Ph--R.sup.2 ( 9X)

Further, the following compounds may be mentioned as examples in whichsome of hydrogen atoms of the 1,4-phenylene group, thetrans-1,4-cyclohexylene group and the 1,4-cyclohexenylene group of A¹,A², A³ and A⁴ are substituted by halogen atoms or cyano groups, or someof ═CH-- groups constituting a ring are substituted by nitrogen atoms,or some of --CH₂ -- groups constituting a ring are substituted by oxygenatoms or sulfur atoms. ##STR12##

The compound of the formula (1) of the present invention is used in theform of a liquid crystal composition prepared by mixing at least onesuch compound with other liquid crystal material and/or a non-liquidcrystal material, whereby the liquid crystal composition can be made tohave a low viscosity, and it is possible to attain a high speed responsewhen the composition is formed into a liquid crystal display device.

The material which may be mixed with the compound of the presentinvention, includes, for example, the following compounds. In thefollowing formulas, each of R^(C) and R^(D) represents an alkyl group,an alkoxy group, halogen atom or a cyano group, provided that "--NON--"represents an azoxy group.

R^(c) --Cy--Cy--R^(D)

R^(c) --Cy--Ph--R^(D)

R^(c) --Ph--Ph--R^(D)

R^(c) --Cy--COO--Ph--R^(D)

R^(c) --Ph--COO--Ph--R^(D)

R^(c) --Cy--CH═CH--Ph--R^(D)

R^(c) --Ph--CH═CH--Ph--R^(D)

R^(c) --Cy--CH₂ CH₂ --Ph--R^(D)

R^(c) --Ph--CH₂ CH₂ --Ph--R^(D)

R^(c) --Ph--N═N--Ph--R^(D)

R^(c) --Ph--NON--Ph--R^(D)

R^(c) --Cy--COS--Ph--R^(D)

R^(c) --Cy--Ph--Ph--R^(D)

R^(c) --Cy--Ph--Ph--Cy--R^(D)

R^(c) --Ph--Ph--Ph--R^(D)

R^(c) --Cy--COO--Ph--Ph--R^(D)

R^(c) --Cy--Ph--COO--Ph--R^(D)

R^(c) --Cy--COO--Ph--COO--Ph--R^(D)

R^(c) --Ph--COO--Ph--COO--Ph--R^(D)

R^(c) --Ph--COO--Ph--OCO--Ph--R^(D) ##STR13##

These compounds are given merely as examples. The ring structures orhydrogen atoms of the terminal groups may be substituted by halogenatoms, cyano groups or methyl groups, and the cyclohexane rings or thebenzene rings may be replaced by other six-membered or five-memberedrings such as pyridine rings or dioxane rings. Further, the linkinggroup between the adjacent rings may be changed. Thus, various materialsmay be approximately selected for use depending upon the desiredproperties.

The liquid crystal composition containing the compound of the presentinvention may be injected into a liquid crystal cell, so that it isinterposed between substrates provided with electrodes, to constitute aliquid crystal electro-optical device.

A typical liquid crystal cell may be a twisted nematic (TN) type liquidcrystal electro-optical device. Here, the term "liquid crystalelectro-optical device" is used to express that it is useful not onlyfor application to a display device but also to e.g. a light adjustablewindow, a light shutter or a polarizing exchanger device.

The liquid crystal electro-optical device can be used in various modessuch as a twisted nematic system, a guest-host system, a dynamicscattering system, a phase change system, a DAP system, a doublefrequency drive system and a ferroelectric liquid crystal displaysystem.

Now, a structure of a liquid crystal electro-optical device and aspecific example for the preparation will be described.

On a substrate made of a plastic, glass or the like, an undercoat layerof SiO₂, Al₂ O₃ or the like, or a color filter layer is formed as thecase requires, and then an electrode for In₂ O₃ -SnO₂ (ITO), SnO₂ or thelike is formed thereon, followed by patterning. Then, an overcoat layerof polyimide, polyamide, SiO₂ or Al₂ O₃ is formed as the case requires,followed by orientation treatment. Then, a sealing material is printed,and the periphery is sealed so that the electrode surfaces face to eachother, followed by curing the sealing material to form an empty cell.

To this empty cell, the composition containing the compound of thepresent invention is injected, and the injection inlet is then sealedwith a sealing agent to form a liquid crystal cell. To this liquidcrystal cell, a polarizing plate, a color polarizing plate, a lightsource, a color filter, a semitransparent reflecting plate, a reflectingplate, a photoconducting plate, an ultraviolet ray-preventive filter orthe like may be laminated, letters or designs may be printed, andnonglare treatment may be applied as the case requires, to obtain aliquid crystal electro-optical device.

The above description is intended to show merely the basic structure andthe basic method for preparation of a liquid crystal electro-opticaldevice. Various other structures may be employed, including, forexample, a double layer liquid crystal cell having two liquid crystallayers with a substrate employing double layer electrodes, and an activematrix device using an active matrix substrate having a functionalelement such as TFT or MIM formed thereon.

By using the compound of the present invention for a liquid crystalcomposition, high speed response can be expected also by conducting highduty drive. Therefore, the present invention is effectively applicableto a supertwisted (STN) type liquid crystal electro-optical devicehaving a highly twisted angle, to which an attention has been drawn inrecent years. Further, the present invention is useful also for aguest-host (GH) type liquid crystal display device using multicolorcolorants or a ferroelectric liquid crystal electro-optical device.

The compound of the formula (1) of the present invention can beproduced, for example, by the following method. ##STR14##

In the above formulas, each of A¹, A², A³ and A⁴, which are independentfrom one another, is a cyclic group selected from atrans-1,4-cyclohexylene group, a 1,4-cyclohexenylene group and a1,4-phenylele group. Each of these cyclic groups is unsubstituted orsubstituted by one or more halogen atoms or cyano groups. One or more═CH-- groups constituting rings of such cyclic groups may be substitutedby nitrogen atoms, and one or more --CH₂ -- groups constituting suchrings may be substituted by oxygen atoms or sulfur atoms.

Each of Y¹ and Y² which are independent from each other, is --COO--,--OCO--, --C.tbd.C--, --CH₂ CH₂ --, --CH═CH--, --OCH₂ --, --CH₂ O-- or asingle bond.

Each of m and n, which are independent from each other, is 0 or 1.

Each of R¹ and R², which are independent from each other, is a C₁₋₁₀alkyl group, a halogen atom or a cyano group. In the case of an alkylgroup, an oxygen atom, a carbonyloxy group or an oxycarbonyl group maybe interposed in a carbon-carbon bond in this alkyl group or in thecarbon-carbon bond between this alkyl group and the cyclic group.Further, some of carbon-carbon bonds in the alkyl group may be triplebonds or double bonds. Furthermore, one --CH₂ -- group in the alkylgroup may be substituted by a carbonyl group, and some or all ofhydrogen atoms in the alkyl group may be substituted by fluorine atoms.

X is a bromine atom or an iodine atom.

Chlorotrifluoroethylene of the formula (10) is treated with n-butyllithium and then reacted with chlorotrimethylsilane of the formula (11)to obtain 1,1,2-trifluoro-2-trimethylsilylethylene of the formula (12).Then, without isolation, this compound (12) is reacted further with alithium compound of the formula (13) to obtain a difluoroethylenecompound of the formula (14).

The obtained compound (14) is hydrolyzed with water and potassiumfluoride to obtain a difluoroethylene compound of the formula (15). Thiscompound is treated with n-butyl lithium and then reacted with iodine toobtain an iodide compound of the formula (16). Further, an acetylenederivative compound of the formula (17) is reacted thereto in thepresence of a palladium catalyst, copper iodide and triethylamine toobtain a difluoro compound of the formula (1).

To introduce an acyl group to R¹ and R² of the compound of the formula(1), a compound of the formula (1) wherein R¹ and R² are hydrogen atomsand an acyl halide may be subjected to a Friedel-Crafts reaction. Tointroduce a cyano group, a compound of the formula (1) wherein R¹ and R²are bromine atoms or iodine atoms may be reacted with CuCN. Further, tointroduce an ethynylene group (--C.tbd.C--) to Y¹ and Y² of the compoundof the formula (1), a compound of the formula (1) wherein R¹ and R² arebromine atoms or iodine atoms and an alkynyl lithium compound may besubjected to a coupling reaction.

BEST MODE FOR CARRYING OUT THE INVENTION EXAMPLE 1

First step

Into a 500 ml of three-necked flask equipped with a condenser and a gassupply tube, 100 ml of tetrahydrofuran (THF) was charged and cooled to-100° C. Then, 11.7 g (0.1 mol) of chlorotrifluoroethylene wasintroduced thereto. 62.1 ml (0.1 mol) of a n-hexane solution of n-butyllithium (1.61M) was dropwise added thereto over a period of 30 minutes.The mixture was stirred for further 30 minutes, and then 10.9 g (0.1mol) of chlorotrimethylsilane was dropwise added thereto.

After the dropwise addition, the mixture was stirred for one hour. Then,a THF solution of 4-propylphenyl lithium separately synthesized by 24.6g (0.1 mol) of 4-propyl iodobenzene and 62.1 ml (0.1 mol) of a n-hexanesolution of n-butyl lithium (1.61M), was dropwise added thereto at -100°C. The mixture was further stirred for two hours at 0° C. Then, a dilutehydrochloric acid aqueous solution was added thereto. The organic layerwas separated. The aqueous layer was extracted with methylene chloride,and the organic layers were put together and dried. Then, the solventwas distilled off to obtain 19.1 g (yield: 75%) of(Z)-1,2-difluoro-1-(4-propylphenyl)-2-trimethylsilyl ethylene.

    CH.sub.3 CH.sub.2 CH.sub.2 --Ph--CF═CF--Si(CH.sub.3).sub.3

Second step

Then, 19.1 g (0.075 mol) of the obtained(Z)-1,2-difluoro-1-(4-n-propylphenyl)-2-trimethylsilylethylene wasdissolved in 50 ml of acetonitrile, and then 8.70 g (0.15 mol) ofpotassium fluoride and 4.05 g (0.225 mol) of water were added thereto.The mixture was reacted for one hour at 70° C. The reaction mixture wascooled, and then 200 ml of water was added thereto. The mixture wasextracted with methylene chloride. The organic layer was washed with asaturated sodium chloride aqueous solution and dried over CaCl₂. Afterfiltration, the solvent and low boiling substances were distilled off,and the residue was further distilled under reduced pressure to obtain11.3 g (yield: 83%) of (E)-1,2-difluoro-1-(4-propylphenyl)ethylene.

    CH.sub.3 CH.sub.2 CH.sub.2 --Ph--CF═CFH

Third step

Then, 11.3 g (0.062 mol) of the obtained(E)-1,2-difluoro-1-(4-propylphenyl)ethylene was dissolved in 50 ml ofTHF, and the solution was cooled to -78° C. Then, 38.5 ml (0.062 mol) ofa n-hexane solution of n-butyl lithium (1.61M) was dropwise addedthereto over a period of 30 minutes. The mixture was stirred for further30 minutes, and then 15.7 g (0.062 mol) of iodide was added at -78° C.

The mixture was heated to room temperature and stirred for 4 hours, andthen a sodium thiosulfate aqueous solution was added thereto. Theorganic layer was separated. The aqueous layer was extracted withmethylene chloride, and the organic layers were put together and dried.Then, the solvent was distilled off, and the obtained crude oil wasdistilled under reduced pressure to obtain 15.8 g (yield: 83%) of(E)-1,2-difluoro-1-iodo-2-(4-propylphenyl)ethylene.

    CH.sub.3 CH.sub.2 CH.sub.2 --Ph--CF═CFI

Fourth step

Then, 15.8 g (0.051 mol) of the obtained(E)-1,2-difluoro-1-iodo-2-(4-propylphenyl)ethylene and 7.34 g (0.051mol) of 4-propylphenyl acetylene were dissolved in ml of triethylamine,and 0.7 g of Pd(PPh₃)₂ Cl₂ and 0.2 g of CuI were further added thereto.

The mixture was reacted at room temperature for 6 hours.

After the reaction, triethylamine was distilled off, and 100 ml ofmethylene chloride was added. The mixture was washed with a 5%hydrochloric acid aqueous solution and then with water and dried. Then,the solvent was distilled off. The obtained solid was purified by silicagel column chromatography to obtain 11.6 g (yield: 70%) of(E)-3,4-difluoro-1,4-bis(4-propylphenyl)-3-buten-1-yne.

    CH.sub.3 CH.sub.2 CH.sub.2 --Ph--CF═CF--C.tbd.C--Ph--CH.sub.2 CH.sub.2 CH.sub.3 ##STR15##

The analytical results of this compound will be shown below.

    ______________________________________                                        .sup.19 F NMR(CDCl.sub.3)                                                                    -145.2 ppm (d, J.sub.F--F = 134Hz)                             δppm from CFCl.sub.3                                                                   -148.4 ppm (d, J.sub.F--F = 134Hz)                             MS             m/e 324(M.sup.+)                                               IR             1160 cm.sup.-1 (C--F)                                          ______________________________________                                    

In the same manner as in Example 1, the following compounds can beprepared. Here, "--Ph--F" represents a p-fluorophenyl group.

CH₃ --Ph--CF═CF--C.tbd.C--Ph--CH₃

CH₃ CH₂ CH₂ CH₂ CH₂ --Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₂ CH₃

CF₃ --Ph--CF═CF'C.tbd.C--Ph--CF₃

F--Ph--CF═CF--C.tbd.C--Ph--F

CH₃ O--Ph--CF═CF--C.tbd.C--Ph--OCH₃

CH₃ CH₂ CH₂ O--Ph--CF═CF--C.tbd.C--Ph--OCH₂ CH₂ CH₃

CH₂ ═CH--Ph--CF═CF--C.tbd.C--Ph--CH═CH₂

EXAMPLE 2

The reactions were conducted in the same manner as in Example 1 exceptthat in the first step in Example 1, 20.5 g (0.1 mol ) of4-propylcyclohexyl bromide was used instead of 4-propyliodobenzene, toobtain 11.6 g (yield: of(E)-3,4-difluoro-1-(4-propylphenyl)-4-(4-propylcyclohexyl)-3-buten-1-yne.

    CH.sub.3 CH.sub.2 CH.sub.2 --Cy--CF═CF--C.tbd.C--Ph--CH.sub.2 CH.sub.2 CH.sub.3 ##STR16##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 330(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 2, the following compounds can beprepared.

CH₃ --Cy--CF═CF--C.tbd.C--Ph--CH₃

CH₃ CH₂ CH₂ CH₂ CH₂ --Cy--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₂ CH₂ CH₃

CF₃ --Cy--CF═CF--C.tbd.C--Ph--CF₃

F--Cy--CF═CF--C.tbd.C--Ph--F

CH₃ O--Cy--CF═CF--C.tbd.C--Ph--OCH₃

CH₃ CH₂ CH₂ O--Cy--CF═CF--C.tbd.C--Ph--OCH₂ CH₂ CH₃

CH₂ ═CH--Cy--CF═CF--C.tbd.C--Ph--CH═CH₂

EXAMPLE 3

The reactions were conducted in the same manner as in Example 1 exceptthat in the first step of Example 1, 25.0 g (0.1 mol) of4-propylcyclohexene-1-iodo-1-yl was used instead of 4-propyliodobenzene,to obtain 9.8 g (yield: 30%) of(E)-3,4-difluoro-1-(4-propylphenyl)-4-(4-propylcyclohexen-1-yl)-3-buten-1-yne.

CH₃ CH₂ CH₂ --Ch--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃ ##STR17##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 328(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 3, the following compounds can beprepared.

CH₃ --Ch--CF═CF--C.tbd.C--Ph--CH₃

CH₃ CH₂ CH₂ Ch₂ CH₂ --Ch--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₂ CH₃

CF₃ --Ch--CF═CF--C.tbd.C--Ph--CF₃

F--Ch--CF═CF--C.tbd.C--Ph--F

CH₃ O--Ch--CF═CF--C.tbd.C--Ph--OCH₃

CH₃ CH₂ CH₂ O--Ch--CF═CF--C.tbd.C--Ph--OCH₂ CH₂ CH₃

CH₂ ═CH--Ch--CF═CF--C.tbd.C--Ph--CH═CH₂

EXAMPLE 4

The reactions were conducted in the same manner as in Example 1 exceptthat in the first step of Example 1, 23.6 g (0.1 mol) of1,4-dibromobenzene was used instead of the 4-propyliodobenzene, toobtain 13.7 g (yield: 38%) of(E)-3,4-difluoro-1-(4-propylphenyl)-4-(4-bromophenyl)-3-buten-1-yne.

Br--Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃ ##STR18##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 361(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 4, the following compounds can beprepared.

Br--Cy--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

Br--Ch--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

EXAMPLE 5

Into a 300 ml three-necked flask equipped with a condenser, 0.90 g (0.01mol) of CuCN and 50 ml of dry dimethylsulfoxide (DMSO) were introduced,heated to 90° C. and dissolved. Then, a DMSO solution containing 3.61 g(0.01 mol) of(E)-3,4-difluoro-1-(4-propylphenyl)-4-(4-bromophenyl)-3-buten-1-yneobtained in Example 4, was dropwise added thereto under stirring. Then,the mixture was stirred for further one hour at 150° C. and then cooledto room temperature.

200 ml of water was poured thereto. The mixture was extracted withmethylene chloride, and the organic layer was washed with a saturatedsodium chloride aqueous solution and dried over CaCl₂. After filtration,the solvent was distilled off, and the obtained solid was purified bysilica gel column chromatography to obtain 2.52 g (yield: 82%) of(E)-3,4-difluoro-1-(4-propylphenyl)-4-(4-cyanophenyl)-3-buten-1-yne.

NC--Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃ ##STR19##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS          m/e 307(M.sup.+)                                                  IR          1160 cm.sup.-1 (C--F), 2230 cm.sup.-1 (C.tbd.N)                   ______________________________________                                    

In the same manner as in Example 5, the following compounds can beprepared. NC--Cy--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

NC--Ch--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

EXAMPLE 6

The reactions were conducted in the same manner as in Example 1 exceptthat in the first step of Example 1, 17.5 g (0.1 mol) of5-methylpyrimidyl bromide was used instead of 4-propyliodobenzene, toobtain 9.54 g (yield: 32%) of(E)-3,4-difluoro-1-(4-propylphenyl)-4-(5-methylpyrimidin-2-yl)-3-buten-1-yne.

CH₃ --Py--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃ ##STR20##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 298(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 6, the following compounds can beprepared. Here, "--Py--" represents a pyrimidin-2,5-diyl group.

CH₃ CH₂ CH₂ --Py--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ O--Py--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ O--Py--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

EXAMPLE 7

The reactions were conducted in the same manner as in Example 1 exceptthat in the first step of Example 1, 18.1 g (0.1 mol) of2-methyl-5-bromo-1,3-dioxane was used instead of 4-propyliodobenzene, toobtain 9.18 g (yield: of(E)-3,4-difluoro-1-(4-propylphenyl)-4-(5-methyl-1,3-dioxan-2-yl)-3-buten-1-yne.Further, in the following description, "--Do--" represents a1,3-dioxan-2-5-diyl group.

CH₃ --Do--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃ ##STR21##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 306(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 7, the following compounds can beprepared.

CH₃ CH₂ CH₂ --Do--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ O--Do--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ O--Do--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

EXAMPLE 8

The reactions were conducted in the same manner as in Example 1 exceptthat in the first step of Example 1, 32.8 g (0.1 mol) of4-(trans-4-propylcyclohexyl)iodobenzene was used instead of4-propyliodobenzene, to obtain 14.6 g (yield: 36%) of(E)-3,4-difluoro-4-[4-(trans-4-propylcyclohexyl)phenyl]-1-(4-propylphenyl)-3-buten-1-yne.

CH₃ CH₂ CH₂ --Cy--Ph--CF═CF--C.tbd.C--Ph'CH₂ CH₂ CH₃ ##STR22##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 406(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 8, the following compounds can beprepared.

CH₃ CH₂ CH₂ --Ph--Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ --Ph--Cy--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ --Cy--Cy--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ --Ph--Ch--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ --Ch--Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ --Ch--Ch--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

EXAMPLE 9

The reactions were conducted in the same manner as in Example 1 exceptthat in the fourth step of Example 1, 4-propylcyclohexylacetylene wasused instead of 4-propylphenylacetylene, to obtain 8.25 g (yield: 25%)of(E)-3,4-difluoro-1-(4-propylcyclohexyl)-4-(4-propylphenyl)-3-buten-1-yne.

CH₃ CH₂ CH₂ --Ph--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃ ##STR23##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 330(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 9, the following compounds can beprepared.

CH₃ --Ph--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ CH₂ CH₂ --Ph--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

CF₃ --Ph--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

F--Ph--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

CH₃ O--Ph--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ O--Ph--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

CH₂ ═CH--Ph--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

CH₃ --Ph--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ CH₂ CH₂ --Ph--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

CF₃ --Ph--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

F--Ph--CF═CF--C.tbd.CF--Ch--CH₃ CH₂ CH₂

CH₃ O--Ph--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ O--Ph--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

CH₂ ═CH--Ph--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

EXAMPLE 10

The reactions were conducted in the same manner as in Example 1 exceptthat in the first step of Example 1, 20.5 9 (0.1 mol) of4-propylcyclohexyl bromide was used instead of 4-propyliodobenzene, andin the fourth step, 4-propylcyclohexylacetylene was used instead of the4-propylphenylacetylene, to obtain 7.39 9 (yield: 22%) of(E)-3,4-difluoro-l,4-bis(4-propylcyclohexyl)-3-buten-1-yne.

CH₃ CH₂ CH₂ --Cy--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃ ##STR24##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 336(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 10, the following compounds can beprepared.

CH₃ --Cy--CF═CF--C.tbd.C--Cy--CH₂ --CH₂ CH₃

CH₃ CH₂ CH₂ CH₂ CH₂ --Cy--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

CF₃ --Cy--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

F--Cy--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

CH₃ O--Cy--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ O--Cy--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

CH₂ ═CH--Cy--CF═CF--C.tbd.C--Cy--CH₂ CH₂ CH₃

CH₃ --Ch--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ CH₂ CH₂ --Ch--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

CF₃ --Ch--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

F--Ch--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

CH₃ O--Ch--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

CH₃ CH₂ CH₂ O--Ch--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

CH₂ ═CH--Ch--CF═CF--C.tbd.C--Ch--CH₂ CH₂ CH₃

EXAMPLE 11

Into a 100 ml three-necked flask equipped with a reflux condenser, 0.139 (0.0055 mol) of magnesium and 10 ml of dry THF were introduced underan argon atmosphere. Then, a few drops of 1-bromopropane was addedthereto, and 1.019 (0.0055 mol) of 4-methylphenethyl bromide was furtherdropwise added at a rate where heat generation continued. Aftercompletion of the dropwise addition, the mixture was refluxed forfurther one hour and then left to cool to room temperature.

Separately, into a 100 ml three-necked flask equipped with a refluxedcondenser, 1.81 9 (0.005 mol) of(E)-3,4-difluoro-1-(4-propylphenyl)-4-(4-bromophenyl)-3-buten-1-yneobtained in Example 4 and 20 ml of a dry THF solution containing 0.19 of1,3-bis(diphenylphosphino)propanedichloronickel [NiCl₂ (dppp)] wereintroduced under an argon atmosphere, and the above solution wasdropwise added thereto by means of a dropping funnel.

After the dropwise addition, the mixture was stirred at room temperaturefor 24 hours. Then, 20 ml of water was added thereto. Further, 20 ml of20% hydrochloric acid was added. Then, the organic layer was separated,washed with water and dried, and then the solvent was distilled off. Theobtained crude product was purified by silica gel column chromatographyto obtain 0.90 g (yield: 45%) of(E)-3,4-difluoro-1-(4-propylphenyl)-4-[4-(4-methylphenethyl)phenyl]-3-buten-1-yne.

CH₃ --Ph--CH₂ CH₂ --Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃ ##STR25##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 400(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 11, the following compounds can beprepared.

CH₃ --Ph--CH₂ CH₂ --Cy--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ --Ph--CH₂ CH₂ --Ch--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ O--Ph--CH₂ CH₂ --Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

EXAMPLE 12

The reactions were conducted in the same manner as in Example 11 exceptthat in Example 11, 1.08 g (0.0055 mol) of1-bromo-2-(4-methylphenyl)ethene was used instead of 4-methylphenethylbromide, to obtain 1.00 g (yield: 50%) of(E)-3,4-difluoro-1-(4-propylphenyl)-4-[4-(2-p-methylphenylethenyl)phenyl]-3-buten-1-yne.

CH₃ --Ph--CH═CH--Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃ ##STR26##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 398(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 12, the following compounds can beprepared.

CH₃ --Ph--CH═CH--Cy--CF═CF--C.tbd.C--Ph--CH₃

CH₃ --Ph--CH═CH--Ch--CF═CF--C.tbd.C--Ph--CH₃

CH₃ O--Ph--CH═CH--Ph--CF═CF--C.tbd.C--Ph--OCH₃

EXAMPLE 13

Into a 100 ml three-necked flask, 2.86 g of cuprous iodide, 4.33 g(0.012 mol) of(E)-3,4-difluoro-1-(4-propylphenyl)-4-(4-bromophenyl)-3-buten-1-yneobtained in Example 4 and 30 ml of dry THF were charged under an argonatmosphere, followed by stirring at room temperature. Then, 1.42 g ofn-butylamine and 1.53 g of p-toluylacetylene were added thereto. Then,10 ml of a dry THF solution containing 0.69 g of (Ph₃ P)₄ Pd was addedthereto, and the mixture was stirred at room temperature for 2 hours.After an addition of 30 ml of a saturated NaHCO₃ aqueous solution, themixture was subjected to liquid separation, and then extracted withmethylene chloride. The solvent was distilled off, and the residue waspurified by silica gel column chromatography to obtain 3.09 g (yield:65%) of(E)-3,4-difluoro-1-(4-propylphenyl)-4-[4-(2-p-toluylethynyl)phenyl]-3-buten-1-yne.

CH₃ --Ph--C.tbd.C--Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃ ##STR27##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 396(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 13, the following compounds can beprepared.

CH₃ --Ph--C.tbd.C--Cy--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ --Ph--C.tbd.C--Ch--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ O--Ph--C.tbd.C--Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

EXAMPLE 14

The reactions were conducted in the same manner as in Example 1 exceptthat in the first step of Example 1, 30.4 9 (0.1 mol) of4-iodophenyltetrahydropyranyl ether was used instead of4-propyliodobenzene, and the product was finally treated with an acid,to obtain 8.05 (yield: 27%) of(E)-3,4-difluoro-4-(4-hydroxylphenyl)-1-(4-propylphenyl)-3-buten-1-yne.

HO--Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

Then, 1.49 g (0.005 mol) of the obtained(E)-3,4-difluoro-4-(4-hydroxyphenyl)-1-(4-propylphenyl)-3-buten-1-yne,1.52 g of potassium carbonate and 30 ml of acetone were added. Further,2.79 g of α-bromo-p-xylene was dropwise added thereto at roomtemperature. The mixture was refluxed for 4 hours, then cooled andfiltered. Then, the solvent was distilled off, and the obtained crudecrystals were purified by silica gel column chromatography to obtain1.71 g (yield: 85%) of(E)-3,4-difluoro-4-[4-(4-methylbenzyloxy)phenyl-1-(4-propylphenyl)-3-buten-1-yne.

CH₃ --Ph--CH₂ O--Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃ ##STR28##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS                m/e 402(M.sup.+)                                            IR                1160 cm.sup.-1 (C--F)                                       ______________________________________                                    

In the same manner as in Example 14, the following compounds can beprepared.

CH₃ --Ph--CH₂ O--Cy--CF═CF--C.tbd.C--Ph--CH₃ CH₂ CH₂

CH₃ --Ph--CH₂ O--Ch--CF═CF--C.tbd.C--Ph--CH₃ CH₂ CH₂

CH₃ O--Ph--CH₂ O--Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

EXAMPLE 15

1.49 g (0.005 mol) of(E)-3,4-difluoro-4-(4-hydroxyphenyl)-1-(4-propylphenyl)-3-buten-1-yneobtained in Example 14 was dissolved in 20 ml of CH₂ Cl₂, and 0.87 g ofpyridine was added thereto at room temperature. The mixture was cooledto 0° C., and then 1.70 g of p-toluic acid chloride was dropwise addedthereto.

The mixture was stirred at room temperature for one hour and cooled, andthen dilute hydrochloric acid was added thereto, followed by filtration.Then, the solvent was distilled off, and the obtained crude crystalswere purified by silica gel column chromatography to obtain 1.87 g(yield: 90%) of(E)-3,4-difluoro-4-[4-(4-methylbenzoyloxy)]-1-(4-propylphenyl)-3-buten-1-yne.

CH₃ --Ph--COO--Ph--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃ ##STR29##

The analytical results of this compound will be shown below.

    ______________________________________                                        MS         m/e 416(M.sup.+)                                                   IR         1160 cm.sup.-1 (C--F) , 1720 cm.sup.-1 (C═O)                   ______________________________________                                    

In the same manner as in Example 15, the following compounds can beprepared.

CH₃ --Ph--COO--Cy--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₃ --Ph--COO--Ch--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CH₂ O--Ph--COO--Ph--CF═CF--C.tbd.C--Ph--CH₃ CH₂ CH₂

EXAMPLE 16

Into a 200 ml three-necked flask, 1.34 g of Pd(PPh₃)₂ Cl₂, 0.37 g of CuIand 100 ml of triethylamine were charged under an argon atmosphere, and4.7 g (0.04 mol) of 4-ethynyl toluene was dropwise added at roomtemperature. After stirring the mixture for 15 minutes, 8.4 g (0.04 mol)of iodotrifluoroethylene was further dropwise added thereto, and themixture was reacted at room temperature for 20 hours.

After filtration, triethylamine was distilled off, and 100 ml ofmethylene chloride was added to the residue. The mixture was washed witha 5% hydrochloric acid aqueous solution and then with water, and dried.Then, the solvent was distilled off. The obtained crude oil was purifiedby silica gel column chromatography to obtain 4.0 g (yield: 51%) of1-p-toluyl-3,4,4-trifluoro-3-buten-1-yne.

CH₃ --Ph--C.tbd.C--CF═CF₂

Then, into a 100 ml three-necked flask, 5.0 g (0.021 mol) of3-fluoro-4-iodotoluene and 50 ml of dry ether were charged under anargon atmosphere, and cooled to -78° C. Then, 13.7 ml (0.022 mol) of an-hexane solution of n-butyl lithium (1.61M) was dropwise added theretoover a period of 15 minutes. Then, the mixture was further stirred for30 minutes, and then the THF solution of 2.77 g (0.014 mol) of thepreviously obtained 1-p-toluyl-3,4,4-trifluoro-3-buten-1-yne, wasdropwise added thereto at -78° C.

Further, the temperature was raised to room temperature, and the mixturewas stirred for one hour. Then, a 1N aqueous solution was added thereto.The organic layer was separated. The aqueous layer was extracted withmethylene chloride. The organic layers were put together and dried.Then, the solvent was distilled off, and the obtained crude oil waspurified by silica gel column chromatography. The obtained solid wasrecrystallized from methanol to obtain 1.24 g (yield: 31%) of(E)-3,4-difluoro-1-(p-toluyl)-4-(2-fluoro-4-methylphenyl)-3-buten-1-yne.Here, "Ph(F)" represents a 2-fluoro-1,4-phenylene group.

CH₃ --Ph(F)--CF═CF--C.tbd.C--Ph--CH₃ ##STR30##

The analytical results of this compound will be shown below.

    ______________________________________                                        .sup.19 F NMR(CDCl.sub.3)                                                                    -110.9 ppm (m)                                                 δppm from CFCl.sub.3                                                                   -137.0 ppm(d, d, J.sub.F--F = 140 Hz)                                         -146.6 ppm(d, d, J.sub.F--F = 140 Hz)                          .sup.1 H NMR(CDCl.sub.3)                                                                     2.40 ppm(s, 6H)                                                δppm from (CH.sub.3).sub.4 Si                                                          7.20 ppm(m, 7H)                                                MS             m/e 286(M.sup.+)                                               IR             2204 cm.sup.-1 (C.tbd.C)                                                      1160 cm.sup.-1 (C--F)                                          ______________________________________                                    

With respect to(E)-3,4-difluoro-1-(p-toluyl)-4-(2-fluoro-4-methylphenyl)-3-buten-1-yneobtained in Example 16, the maximum absorption wavelength of theabsorption band appearing in the ultraviolet absorption region, wasmeasured and found to be 300 nm.

For the measurement of the ultraviolet absorption spectrum,self-recording spectrophotometer UV-3100 (manufactured by ShimadzuCorporation) was employed, and cyclohexane was used as the solvent. Theconcentration of the sample was 1×10⁻⁵ mol/l, and the measurement wasconducted by using a quartz cell having a path length of 1 cm. At thattime, the background correction was made with reference to atmosphericair, and the slit width was 2 nm. The measured wavelength region rangedfrom 500 nm on the long wavelength side to 200 nm on the shortwavelength side.

On the other hand, the maximum absorption wavelength oftrans-1,2-difluoro-l,2-bis(4-methoxyphenyl)ethylene was 310 nm, and thiscompound thus had the maximum absorption wavelength on the shortwavelength side, as compared withtrans-1,2-difluoro-1,2-bis(4-methoxyphenyl)ethylene.

Thus, the ultraviolet wavelength distribution of the sunlight whichrises from about 290 nm and the intensity of light of which increasestowards the long wavelength overlaps little with the ultravioletabsorption region of the difluoro compound of the present invention,whereby the compound of the present invention has improved stabilityagainst ultraviolet rays.

In the same manner as in Example 16, the following compounds can beprepared. Here, "Ph(F)" represents a 2-fluoro-1,4-phenylene group.

CH₃ CH₂ CH₂ --Ph(F)--CF═CF--C.tbd.C--Ph--CH₂ CH₂ CH₃

CF₃ --Ph(F)--CF═CF--C.tbd.C--Ph--CF₃

F--Ph(F)--CF═CF--C.tbd.C--Ph--F

CH₃ O--Ph(F)--CF═CF--C.tbd.C--Ph--OCH₃

CH₃ CH₂ CH₂ O--Ph(F)--CF═CF--C.tbd.C--Ph--OCH₂ CH₂ CH₃

CH₂ ═CHCH₂ --Ph(F)--CF═CF--C.tbd.C--Ph--CH₂ CH═CH₂

EXAMPLE 17

To 80 wt % of a liquid crystal composition "ZLI-1565" manufactured byMerck Co., 20 wt % of the compound obtained in Example 16 of the presentinvention was added to obtain a liquid crystal composition, and itsliquid crystal physical property values were measured. The results areshown in Table 1. Further, for the purpose of comparison, the liquidcrystal physical property values of ZLI-1565 will also be shown.

                  TABLE 1                                                         ______________________________________                                                     Liquid crystal composition                                       Liquid crystal                                                                             containing the compound                                          physical     obtained in Example 16 of                                        properties   the present invention                                                                          ZLI-1565                                        ______________________________________                                        N-I point (Tc)                                                                             77.3° C.  86.4° C.                                 Δn     0.162            0.123                                           Viscosity at 25° C.                                                                 14.7             15.4                                            (cSt)                                                                         Viscosity at 0° C.                                                                  57.5             59.2                                            (cSt)                                                                         ______________________________________                                    

As is evident from Table 1, the liquid crystal composition containingthe compound of the present invention is superior to the conventionalcomposition. EXAMPLE 18

To 80 wt % of a liquid crystal composition "ZLI-1565" manufactured byMerck Co., 20 wt % of the compound obtained in Example 1 of the presentinvention was added to obtain a liquid crystal composition. AsComparative Examples, a liquid crystal composition composed solely ofthe liquid crystal composition "ZLI-1565" manufactured by Merck Co.(Comparative Example 1) and a liquid crystal composition prepared byadding 20 wt % of trans-4,4'-bis-(n-propyl)difluorostilbene to 80 wt %of the liquid crystal composition "ZLI-1565" manufactured by Merck Co.(Comparative Example 2) were prepared. These liquid crystal compositionswere respectively sealed in liquid crystal cells provided withpolarizing plates to obtain STN type liquid crystal display devices.

The display properties of the liquid crystal display devices of thisExample and Comparative Example 1 were almost equal, and high speedresponses were obtained as compared with the device of ComparativeExample 2. Then, the liquid crystal display devices of this Example andComparative Example 2 were irradiated by an ultraviolet ray carbon arclamp for 200 hours. After irradiation, the liquid crystal compositionsin the respective devices were analyzed.

As a result, in the case of the liquid crystal composition of thisExample, no substantial formation of a new compound was observed. On theother hand, in the case of the liquid crystal composition of ComparativeExample 2, generation of cis-4,4'-bis-(n-propyl)difluorostilbene wasobserved.

INDUSTRIAL APPLICABILITY

The compound of the formula (1) of the present invention has a lowviscosity and when used as a liquid crystal composition, it improves theresponse speed even when added in a small amount, whereby low voltagedrive, high duty drive and wide temperature range operation will be madepossible.

    R.sup.1 --(A.sup.1 --Y.sup.1).sub.m --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --(Y.sup.2 --A.sup.4).sub.n --R.sup.2                     (1)

provided that in the formula (1), A¹, A², A³, A⁴, Y¹, Y², m, n, R¹ andR² are as follows:

each of A¹, A², A³ and A⁴, which are independent from one another, is acyclic group selected from a trans-1,4-cyclohexylene group, a1,4-cyclohexenylene group and a 1,4-phenylene group, wherein each ofsuch cyclic groups is unsubstituted or substituted by one or morehalogen atoms or cyano groups, one or more ═CH-- groups constitutingrings of such cyclic groups may be substituted by nitrogen atoms, andone or more --CH₂ -- groups constituting rings of such cyclic groups maybe substituted by oxygen atoms or sulfur atoms;

each of Y¹ and Y² which are independent from each other, is --COO--,--OCO--, --C.tbd.C--, --CH₂ CH₂ --, --CH═CH--, --OCH₂ --, --CH₂ O-- or asingle bond;

each of m and n, which are independent from each other, is 0 or 1; and

each of R¹ and R² which are independent from each other, is a C₁₋₁₀alkyl group, a halogen atom or a cyano group, provided that in the caseof the alkyl group, an oxygen atom, a carbonyloxy group or anoxycarbonyl group may be interposed in a carbon-carbon bond of the alkylgroup or in a carbon-carbon bond between this alkyl group and theadjacent cyclic group, some of carbon-carbon bonds in the alkyl groupmay be triple bonds or double bonds, one --CH₂ -- group in the alkylgroup may be substituted by a carbonyl group, and some or all ofhydrogen atoms in the alkyl group may be substituted by fluorine atoms.

Further, its durability against e.g. ultraviolet rays is higher than adifluorostilbene type liquid crystal, and its characteristic of lowviscosity can be sufficiently utilized.

We claim:
 1. A difluoro-derivative compound of the following formula(1):

    R.sup.1 --(A.sup.1 --Y.sup.1).sub.m --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --(Y.sup.2 --A.sup.4).sub.n --R.sup.2                     ( 1)

provided that in the formula (1), A¹, A², A³, A⁴, Y¹, Y², m, n, R¹ andR² are as follows: each of A¹, A², A³ and A⁴, which are independent fromone another, is a cyclic group selected from the group consisting of atrans-1, 4 -cyclohexylene group, a 1,4 -cyclohexenylene group and a1,4-phenylene group, at least one of A² and A³ being atrans-1,4-cyclohexylene group, wherein each of such cyclic groups isunsubstituted or substituted by one or more halogen atoms or one orhalogen atoms or cyano groups, one or more ═CH-- groups constitutingrings of such cyclic groups can be substituted by nitrogen atoms, andone or more --CH.sub. 2-- groups constituting rings of such cyclicgroups can be substituted by oxygen atoms or sulfur atoms; each of Y¹and Y², which are independent from each other, is --COO--, --OCO--,--C.tbd.C--, --CH₂ CH₂ --, --CH═CH--, --OCH₂ --, --CH₂ O-- or a singlebond; each of m and n, which are independent from each other, is 0 or 1;and each of R¹ and R², which are independent from each other, is a C₁₋₁₀alkyl group, a halogen atom or a cyano group, provided that in the caseof the alkyl group, an oxygen atom, a carbonyloxy group or an oxycarbonygroup can be interposed in a carbon-carbon bond of the alkyl group or ina carbon-carbon bond between this alkyl group and the adjacent cyclicgroup, some of carbon-carbon bonds in the alkyl group can be triplebonds or double bonds, one --CH₂ -- group in the alkyl group can besubstituted by a carbonyl group, and some or all of hydrogen atoms inthe alkyl group can be substituted by fluorine atoms.
 2. Thedifluoro-derivative compound according to claim 1, which has thefollowing formula (2):

    R.sup.1 --A.sub.2 --CF═CF--C.tbd.A.sup.3 --R.sup.2     ( 2)

provided that in the formula (2), A², A³, R¹ and R² are as defined withrespect to the formula (1).
 3. A compound having a liquid crystalproperty selected from difluoro-derivative compounds of the followingformula (1):

    R.sup.1 --(A.sup.1 --Y.sup.1).sub.m --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --(Y.sup.2 --A.sup.4).sub.n --R.sup.2                     ( 1)

provided that in the formula (1), A¹, A², A³, A⁴, Y¹, Y², m, n, R¹ andR² are as follows: each of A¹, A², A³ and A⁴, which are independent fromone another, is a cyclic group selected from the group consisting of atrans-1,4-cyclohexylene group, a 1,4-cyclohexenylene group and a1,4-phenylene group, at least one of A² and A³ being atrans-1,4-cyclohexylene group, wherein each of such cyclic groups isunsubstituted or substituted by one or more halogen atoms or one orhalogen atoms or cyano groups, one or more ═CH-- groups constitutingrings of such cyclic groups can be substituted by nitrogen atoms, andone or more --CH₂ -- groups constituting rings of such cyclic groups canbe substituted by oxygen atoms or sulfur atoms; each of Y¹ and Y², whichare independent from each other, is --COO--, --OCO--, --C.tbd.C--, --CH₂CH₂ --, --CH═CH--, --OCH₂ --, --CH₂ O-- or a single bond; each of m andn, which are independent from each other, is 0 or 1; and each of R¹ andR², which are independent from each other, is a C₁₋₁₀ alkyl group, ahalogen atom or a cyano group, provided that in the case of the alkylgroup, an oxygen atom, a carbonyloxy group or an oxycarbony group can beinterposed in a carbon-carbon bond of the alkyl group or in acarbon-carbon bond between this alkyl group and the adjacent cyclicgroup, some of carbon-carbon bonds in the alkyl group can be triplebonds or double bonds, one --CH.sub. 2-- group in the alkyl group can besubstituted by a carbonyl group, and some or all of hydrogen atoms inthe alkyl group can be substituted by fluorine atoms.
 4. The compoundaccording to claim 3, which is selected from difluoro-derivativecompounds of the following formula (2):

    R.sup.1 --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --R.sup.2  ( 2)

provided that in the formula (2), R², A³, R¹ and R² are as defined withrespect to the formula (1).
 5. A liquid crystal composition containingat least one difluoro-derivative compound of the following formula (1):

    R.sup.1 --(A.sup.1 --Y.sup.1).sub.m --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --(Y.sup.2 --A.sup.4).sub.n --R.sup.2                     ( 1)

provided that in the formula (1), A¹, A², A³, A⁴, Y¹, Y², m, n, R¹ andR² are as follows: each of A¹, A², A³ and A⁴, which are independent fromone another, is a cyclic group selected from the group consisting of atrans-1,4-cyclohexylene group, a 1,4-cyclohexenylene group and a1,4-phenylene group, at least one of A² and A³ being atrans-1,4-cyclohexylene group, wherein each of such cyclic groups isunsubstituted or substituted by one or more halogen atoms or one orhalogen atoms or cyano groups, one or more ═CH-- groups constitutingrings of such cyclic groups can be substituted by nitrogen atoms, andone or more --CH₂ -- groups constituting rings of such cyclic groups canbe substituted by oxygen atoms or sulfur atoms; each of Y¹ and Y², whichare independent from each other, is --COO--, --OCO--, --C.tbd.C--, --CH₂CH₂ --, --CH═CH--, --OCH₂ --, --CH₂ O-- or a single bond; each of m andn, which are independent from each other, is 0 or 1; and each of R¹ andR², which are independent from each other, is a C₁₋₁₀ alkyl group, ahalogen atom or a cyano group, provided that in the case of the alkylgroup, an oxygen atom, a carbonyloxy group or an oxycarbony group can beinterposed in a carbon-carbon bond of the alkyl group or in acarbon-carbon bond between this alkyl group and the adjacent cyclicgroup, some of carbon-carbon bonds in the alkyl group can be triplebonds or double bonds, one --CH₂ -- group in the alkyl group can besubstituted by a carbonyl group, and some or all of hydrogen atoms inthe alkyl group can be substituted by fluorine atoms.
 6. The liquidcrystal composition according to claim 5, which contains at least onedifluoro-derivative compound of the following formula (2):

    R.sup.1 --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --R.sup.2  ( 2)

provided that in the formula (2), A², A³, R¹ and R² are as defined withrespect to the formula (1).
 7. A liquid crystal electro-optical devicehaving a liquid crystal composition containing at least onedifluoro-derivative compound of the following formula (1):

    R.sup.1 --(A.sup.1 --Y.sup.1).sub.m --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --(Y.sup.2 --A.sup.4).sub.n --R.sup.2                     ( 1)

provided that in the formula (1), A¹, A², A³, A⁴, Y¹, Y², m, n, R¹ andR² are as follows: each of A¹, A², A³, and A⁴, which are independentfrom one another, is a cyclic group selected from the group consistingof a trans-1,4-cyclohexylene group, a 1,4-cyclohexenylene group and a1,4-phenylene group, at least one of A² and A³ being atrans-1,4-cyclohexylene group, wherein each of such cyclic groups isunsubstituted or substituted by one or more halogen atoms or one orhalogen atoms or cyano groups, one or more ═CH-- groups constitutingrings of such cyclic groups can be substituted by nitrogen atoms, andone or more --CH₂ -- groups constituting rings of such cyclic groups canbe substituted by oxygen atoms or sulfur atoms; each of Y¹ and Y², whichare independent from each other, is --COO--, --OCO--, --C.tbd.C--, --CH₂CH₂ --, --CH═CH--, --OCH₂ --, CH₂ O-- or a single bond; each of m and n,which are independent from each other, is 0 or 1; and each of R¹ and R²,which are independent from each other, is a C₁₋₁₀ alkyl group, a halogenatom or a cyano group, provided that in the case of the alkyl group, anoxygen atom, a carbonyloxy group or an oxycarbony group can beinterposed in a carbon-carbon bond of the alkyl group or in acarbon-carbon bond between this alkyl group and the adjacent cyclicgroup, some of carbon-carbon bonds in the alkyl group can be triplebonds or double bonds, one --CH₂ -- group in the alkyl group can besubstituted by a carbonyl group, and some or all of hydrogen atoms inthe alkyl group can be substituted by fluorine atoms.
 8. The liquidcrystal electro-optical device according to claim 7, which has a liquidcrystal composition containing at least one difluoro-derivative compoundof the following formula (2) interposed between substrates provided withelectrodes:

    R.sup.1 --A.sup.2 --CF═CF--C.tbd.C--A.sup.3 --R.sup.2  ( 2)

provided that in the formula (2), A², A³, R¹ and R² are as defined withrespect to the formula (1).
 9. The difluoro-derivative compoundaccording to claim 2, wherein A² is a trans-1,4-cyclohexylene group. 10.The difluoro-derivate compound according to claim 2, wherein A³ is atrans-1,4-cyclohexylene group.
 11. The difluoro-derivative compoundaccording to claim 2, wherein A² and A³ are trans-1,4-cyclohexylenegroups.
 12. The compound having a liquid crystal property according toclaim 4, which is selected from difluoro-derivative compounds, whereinA² is a trans-1,4-cyclohexylene group.
 13. The compound having a liquidcrystal property according to claim 4, which is selected fromdifluoro-derivative compounds, wherein A³ is a trans-1,4-cyclohexylenegroup.
 14. The compound having a liquid crystal property according toclaim 4, which is selected from difluoro-derivative compounds, whereinA² and A³ are trans-1, 4-cyclohexylene groups.
 15. The liquid crystalcomposition according to claim 6, which contains at least onedifluoro-derivative compound, wherein A² is a trans-1,4-cyclohexylenegroup.
 16. The liquid crystal composition according to claim 6, whichcontains at least one difluoro-derivative compound, wherein A³ istrans-1,4-cyclohexylene group.
 17. The liquid crystal compositionaccording to claim 6, which contains at least one difluoro-derivativecompound, wherein A² and A³ are trans-1,4-cyclohexylene groups.
 18. Theliquid crystal electro-optical device according to claim 8, which has aliquid crystal composition containing at least one difluoro-derivativecompound wherein A² is a trans-1,4-cyclohexylene group, interposedbetween substrates provided with electrodes.
 19. The liquid crystalelectro-optical device according to claim 8, which has a liquid crystalcomposition containing at least one difluoro-derivative compound whereinA³ is a trans-1,4-cyclohexylene group, interposed between substratesprovided with electrodes.
 20. The liquid crystal electro-optical deviceaccording to claim 8, which has a liquid crystal composition containingat least one difluoro-derivative compound wherein A² and A³ aretrans-1,4-cyclohexylene groups, interposed between substrates providedwith electrodes.